Conventionally, the following configuration is proposed for the above type of shelving system.
It is configured so that a constant travel path is arranged in a space within a warehouse or a business office, a plurality of shelves (movable shelves) installed for back and forth movement is arranged on the constant travel path leaving a space for a working aisle, a button for specifying the necessary working aisle when the working aisle is necessary between the movable shelves is provided on the movable shelf opposing, for example, the relevant working aisle, and one or a plurality of movable shelves self-advances along the constant travel path until the space between the movable shelves specified in accordance with the operation of the button reaches the width of the working aisle. Workers or cargo vehicles (e.g., fork lift) enter the working aisle opened between the movable shelves, and handling of articles is performed to the movable shelves opposing such working aisle.
When the movable shelf is self-advanced, a width-deviation correction control is performed so that the movable shelf can move along the travel path. For example, in JP-A 2000-142922, a position reference member (e.g., magnetic tape) is laid along the travel path, and by detecting such position reference member with a contact-subjecting position detector (e.g., magnetic sensor) for each movable shelf, the deviation from the travel path of the movable shelf is detected, and the movable shelf can move along the travel path while correcting the detected deviation.
Further, when the movable shelf is self-advanced, an attitude control is performed to maintain the attitude of the movable shelf in a direction perpendicular to the travel path. For example, in JP-A 2001-48314, the moved distances of both ends in the right-and-left direction at right angles to the travel direction of the movable shelf are each detected by counting a pulse of a pulse encoder coupled to traveling wheels of the movable shelf, and attempt is made to eliminate the difference of the moved distances between such ends, that is, to maintain the attitude of the movable shelf in the direction at right angles to the travel path.
In the above-mentioned conventional configuration, when the movable shelf is self-advanced, in order to achieve a shelving system capable of performing both the width-deviation correction control and the attitude control, the position reference member (magnetic tape) must be laid, and the contact-subjecting position detector (magnetic sensor) for detecting the position reference member must be provided on each movable shelf, and further, two pulse encoders must be arranged on each movable shelf to maintain the attitude of the movable shelf in the direction perpendicular to the travel path, thereby arising a problem of increase in cost.
In the movable shelf in which the position reference member is laid, and the contact-subjecting position detector as well as the pulse encoder are provided, when the movable shelf is moved in a tilted manner, the trajectory of the pulse encoder draws an arc, thereby causing an error between the moved distances of both ends and the moved distance in the travel direction, and arising a problem that an accurate attitude control of the movable shelf can not be performed. Further, when the movable shelf is tilted, an error occurs in the moved distance in the direction at right angles to the travel path detected by the contact-subjecting detector.
It is therefore an object of the present invention to provide a shelving system capable of accurately performing the width deviation correction control and the attitude control of a movable shelf and, further, reducing cost.